Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fi
1) Tropomyosin shifts and unblocks the cross- bridge binding sites.
2) Calcium is released and binds to the troponin complex.
3) The sarcoplasmic reticulum is depolarized when a wave of depolarization moves from the neuromuscu junction into the cell's interior by way of the transverse tubules.
4) The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using e from ATP.
5) An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane at the neuromuscular junction.